A hydraulic excavator is a kind of a slewing-type work machine. Generally, the hydraulic excavator consists of a lower travelling mechanism and a upper swiveling mechanism which are connected by a slewing apparatus, the upper swiveling mechanism being adapted to rotate with respect to the lower travelling mechanism. A front working member is provided on the upper swiveling mechanism, the working member being consisted of a boom, an arm and a front attachment. The front attachment is mainly a bucket to be connected to the arm.
Soil and sand excavated by the hydraulic excavator are loaded on a vessel of a dump truck. For this purpose, a dump truck waits at a position which is apart a predetermined distance from the hydraulic excavator, excavated soil and sand being loaded from the hydraulic excavator on the vessel of the dump truck. The hydraulic excavator performs repeatedly the excavation of soil and sand, and loading them on the vessel of the dump truck. The slewing apparatus is mounted to carry out the repeated performance of the hydraulic excavator.
The hydraulic excavator executes swiveling action so that it is necessary to ensure safety of surroundings. That is, the hydraulic excavator is necessary to pay attention not to contact with some obstacle at a time of swiveling action of the hydraulic excavator. For example, when the hydraulic excavator makes swiveling action in such a situation that the dump truck is extremely approached to the hydraulic excavator, a counterweight of the hydraulic excavator being brought into contact with the dump truck. An operator who operates the hydraulic excavator cannot find visually as to whether or not the counterweight causes interference, due to the counterweight is positioned rearward direction of an operator's cab.
Dead angle zone comes into existence specifically to the backward direction for an operator who is boarded in an operator's cab, and also dead angle is produced for left side and right side direction, further also is formed dead angle to the front side thereof. For this purpose, a patent document 1 discloses a technology that plural cameras are mounted on a hydraulic excavator for displaying an overhead view image by means of signal process of the images taken from the cameras. In accordance with this technology, virtual image of overhead view from upper position to downwardly can be displayed by performing coordinate transformation of images taken by the cameras, the surrounding situation can be recognized by the operator in the manner of high visibility. Especially, under the situation that any obstacle is placed at a closed position from the hydraulic excavator, it is extremely important technology to make intuitively recognition for the operator as to the distance between the hydraulic excavator and the obstacle.